Firearms have been used by people for centuries. Aiming aids such as sights, crosshairs, or telescopes have been added to various firearms to assist the shooter in pointing the gun at a target.
Since the projectiles shot from a gun have a limited velocity, they drop in a curve (typically an asymmetric parabolic curve). Thus, when shooting at a stationary target, the sight on a gun will be set to aim the barrel (i.e., a straight line extending from the axis of the barrel) above the target by an amount that compensates for the drop in the projectile as it travels the distance to the target.
Moving targets present a more difficult problem. Since the target will have moved some distance left, right, up, or down (and perhaps closer or further away) between the time the projectile is launched and the time the projectile reaches the target, the barrel will have to be pointed to lead the target in its direction of travel. A closer target will require a smaller amount of lead angle than a target further away. A slower target will require a smaller amount of lead than a faster target. With prior-art sights, it has been quite difficult to estimate the size of lead angle to provide.
U.S. Pat. No. 4,112,583, “GUN LEAD SIGHT” issued Sep. 12, 1978 to Castilla describes a lead sight with numbers, corresponding to the numbered shooting positions on a standard skeet range, printed on a transversely extended transparent member mounted by a strap above gun barrels toward the muzzle end. “High” and “Low”, also imprinted on the transparent member, correspond to the high house and the low house from which the clay pigeons are released. Such a lead sight purportedly helps the beginner in skeet shooting to lead the skeet clay “bird” properly and helps the experienced shooter having a problem with one or more positions. While perhaps useful for skeet where the target is always at a fixed distance, such a gun sight is much less useful for hunting real game where the target is at various ranges and differing speeds.
U.S. Pat. No. 1,421,553, “GUN SIGHT” issued Jul. 4, 1922 to Pohl describes a lead sight useful for a shotgun, whereby the target object may be sighted while in motion and the shot fired at a lead angle in advance of the target such that the distance traveled by the target during the flight of the shot after discharge of the gun is compensated by the lead angle of the barrel when fired. This sight is formed by a transversely mounted bar having a plurality of bore-hole sight openings formed at different angles (each formed at a different radial angle), the radius center point corresponding to the position of the hunter's eye in sighting along the center ridge. The sight openings are each the same size and shape, other than being at differing angles. The marksman is left with the duty to judge the distance to the object and its speed (e.g., that a bird is flying 350 feet away and at a speed that would need a sight line about eight feet in front of the bird). This would be a difficult judgment task for a hunter in the field hunting real game where the target is at various ranges and differing speeds.
U.S. Pat. No. 3,178,824, “SHOT GUN SIGHTING DEVICE” issued Feb. 16, 1961 to Callihoe describes an elliptical shotgun lead sight with radially extending lines and different sized concentric ellipses. This device also leaves the marksman with the problem of judging distance to the object and its speed.
What is needed is a sight better configured to assist the shooter in estimating the size of lead angle to provide for a given moving target, and to help automatically point the barrel of the gun at the appropriate angle to the target.